Excitons in C-60 studied by temperature-dependent optical second-harmonic generation

Article

关键词: METAL-DOPED C-60;    SOLID C-60;    FULLERENE C-60;    ABSORPTION-SPECTRA;    C60;    TRANSITIONS;    FILMS;    GAP;   

DOI  :  10.1103/PhysRevB.52.17158

来源: SCIE

【 摘 要 】

The electric-dipole-forbidden T-1(1g) excitonic state of solid C-60 at hw=1.81 eV can be probed with a second-harmonic generation (SHG) experiment. We show that the SHG line shape depends strongly on the degree of rotational order. We observe a splitting into two peaks below the rotational ordering phase-transition temperature of 260 K. The origin of this splitting is discussed in terms of a possible Jahn-Teller effect, a possible Davydov splitting due to the four molecules per unit cell in the low-temperature phase, and a mixing of the nearly degenerate T-1(1g) and (1)G(g) free molecule states because of the lower symmetry in the solid. The exciton band structure is calculated with a charge-transfer-mediated propagation mechanism as suggested by Lof et al.(2) and with one-electron (-hole) transfer integrals determined from band-structure calculations. Comparison with our experimental SHG data leads to a reasonable agreement and shows that a mixing of (1)T(1)g and (1)G(g) states may explain the splitting at low temperature.

【 授权许可】

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